Electric measuring instrument for iron-loss testing.



L. W. CHUBB.

ELECTRIC MEASURING INSTRUMENT FOR IRON LOSS TESTING.

APPLICATION FTLED MAY 24, 1909.

1,170,607. rammed Feb. 8,1916

25 H. v T ii? T a? WITNESSES: Z5 |N ENTOR I BY I ATTORNEY thischaracter.

UNTTED snares rarnnr c arion,

IJEIVIS W. CHUBB, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC AND MANTTFACTURTNG COMPAN-Y. A CORPORATION OF PENNSYLVANIA.

ELECTRIC MEASURING INSTRUMENT FOR IRON-LOSS TESTING.

To all whom it "may concern Be it known that I, Lewis N. Curran, acitizen of the United States, and aresident of \Vilkinsburg, in thecounty of Allegheny and State of Pennsylvania, have invented a new anduseful Improvement in. Elcctri c llleasuring Instruments for Iron-LossTesting, of which the following is a specification, this applicationbeing a continuation, in part, of my application Serial-No. 467,480,filed December 14, 1908.

My invention relates to electrical measuring instruments for testing oftransformers and other electromagnetic apparatus employing alternatingmagnetic fluxes iniron circuits, and it has special reference to suchapparatus and methods as are adapted to determine the iron or corelosses in devices of The object of my invention is to provide animproved measuring instrument that shall give adi'rect indication of thesquare-rootof-the-niean-square value of the instantaneous electromotiveforces of a source of alternating current electricityhaving a. sine wavecharacteristic, which would cause the same iron loss in a. transformeras is caused by the circuit to-Which the instrument is connected,irrespective of the electromotive force wave form of said circuit, theloss in the instrument being indicated on a separate dial by the samepointer, as hereinafter explained.

According to a well known method of obtaining the core losses intransformers, all or part of the winding is supplied with su'l'licientalternating current to cause a cyclic magnetization of sufficientmagnitude to induce, 'atthe terminals, the standard voltage for whichthe transformer is designed.

Vith a voltmeter and the pressure coil of a wattmeter connected acrossthe terminals and an ammeter and the series coil of the \vattmeterconnected in series with the suppl'y circuit, the readingnf thewattmeter has heretofore been taken as an indication of the iron loss atthe voltage indicated by the voltmeter. 1

The core loss is dependent upon the wave form of the impressedelectromotive force, a peaked wave giving-"a somewhat lower coreSpecification. of Letters Patent.

Patented Feb. 8, ti-H6.

Application filed May 24, 1909. Serial No. 497,972.

loss than a sine wave, and a flat wave giving a somewhat higher coreloss than a sine wave, and, since the wave forms of alternatin g currentgenerators usually vary, more or less, from the sine wave, core losstests on diflerent supply circuits often differ from 10% to 15% from thevalue obtained on a sine wave, such differences depending upon how muchthe fiunlamcntal wave of the genorator varies from a true sine Wave andhow much additional distortion may be caused by resistance andinductance in the armasupply the losses.

The aforesaid result is accomplished by my invention which consists of anovel voltmeter which, when connected to a testing circuit, indicatesdirectly the square-root-of themean-square of the instantaneouselectromotiveforees of a sine wave, which would cause the same loss in atransformer as the electromotive force wave of the circuit to which theinstrument is connected. With this instrument, therefore, the sine waveloss may be obtained, on any reasonably distorted wave, without knowingthe form factor, or the amount of distortion.

The total losses in transformer cores are made up of a hysteresis loss,which depends upon the average value of the impressed voltage, and aneddy current loss, which is dependent upon the square-root-of-themeanloss would be obtained, but the eddy current loss would be too high,thus giving a total loss which is too high. The instrument embodying myinvention indicates a value of voltage which is such a function of boththe a verage and the scum re-root-ot-the-meansquare value of theinstantaneous electromotive forces that the error in the hysteresis lossis equal to and opposite to the error in eddy current loss and.therefore, the total measured loss correct and equal to the loss whichwould be obtained on a sine wave of voltage.

My improved meter comprises, in general, a closed nmgnetie circuit ofiron preferably built 11 i of a series of thin. rin 'iunchin s havingsuch a relation of eddy current and hysteresis losses that when thelosses in tllu stationary and movable coils and in the resistance aretaken into account the ratio of the total eddy current loss to the totalhysteresis loss corresponds to that of an ordinary transformer. It therelation of losses in the transformer and in the instrument agreeprecisely, the instrument readings should be absolutely correct butquite wide variations in this relation will introduce no appreciableerror on the usual testing waves.

l igure 1 oil? the accompanying drawings is a diagrammatic view of aniron loss volt meter embodyingmy invention. Fig. 2 is a diagram showingthe circuit connections of a testing" system utilizing; the iron lossvoltmeter of Fig. 1, and Fig. 3 is a diagram of a modified arrangementsimilar to that of Fig.

Although I have illustrated my improvement in connection with a zeroreading meter, which is constructed on the Kelvin balance principle,other types of instruments may obviously be employed within the, scopeof my invention.

Reierring' to the drawings, the iron loss voltmeter of F 1g. 1 comprisesa magnetizable core member, 1, a wii'iding 2 associated therewith,stationary coils 3, 4-, 5 and 6, movable coils 7 and 8, a Zero readingpointer 9 attached to the movable member, a spring 10' and an adjustingknob 11 for opposing the torquev of the movable member, a pointer 12attached to the knob 11, a resistance 13, auxiliary coils 14, 15, 16 andl? by means of which the instrun'ient is made to read the loss in bothits shunt an: :lSSCIlGS circuits, and dials 1S and 19 which resiiectively indi cate the voltage which would give the ame loss in atransformer when tested on a sin; wave, and the watts lost in theinstrument,

' itself.

A series circuit is established from one terminal 20 of the meterthrough conductor 21, stationary coils 4, 5, 6 and 3, winding 2 andconductor 22 to the opposite terminal 23 of the meter. A shunt circuitis established from conductor 21 through auxiliary coils 15, 16, 1'? and14, moving coils 7 and 8 and resistance 13 to the conductor 22. The aniliary coils 11, 15, 16 and 17 have the same number of turns as thestationary coils 8, 4L, 5 and 6 in order that the total losses in theinstrun'ient may iniiuence the torque of the meter. Under theseconditions the dial 19, when properly calibrated, will correctly in--dicate the total loss in the iron loss volt-. meter so that it may bereadily and accurately ascertained and subtracted from the indication ofthe wattmeter 21 when the in strument is connected in circuit, as shownin Fig. 2 oil the drawings. The fact that the losses in the instrumentinfluence its voltage reading does not introduce any error because theselosses are taken into account in proportioning the total hysteresis tothe total eddy current losses in the device. It will be observed thatwith the arrangement shown the shunt circuit of the meter measures thetotal potential drop and at the same time the series coil and theauxiliary coil (taken together, since both react on the movable coil)measure the total. current in the meter.

Referringparticularly to Fig. 2, a trans former 2.7. for which a test isdesired,is eonncctcd to any suitable source of alternating current. suchas single-phase generators 526, the voltage applied to the transformerbQIiIlQ' adjusted by means of an auto-transtorn'i'er 27 having aplurality of taps 28 and a moving contact arm '29. One winding, 30 ofti. transformer is connected across the circuit of the generator throughthe auto-trans :l 'ormer 27. one terminal of the winding bcino'connected to the arm 2!). The iron loss voltmeter is connected acrossthe terminals of a winding 30aud the voltage coil of a wattmeter 24 iseonnected'in multiple circuit with the ironloss voltmeter. A secondwinding 81 of the transformer 25 opencircuited and theauto-trans'toriner 27 adjusted until the.i.ron loss voltmeter indicatesthe standard voltage of the winding; 30 ot' the transformer 25. ,Whcnthis point is reached, the watts lost in the iron loss meter are read onthe dial 19 and. the total watts lost in the voltmeter and in the tranceformer are read on the wattmeter 9 t, thedii terence between these tworeadings is the correct core. loss in watts of the transformer I By theSteinmetz formula the hysteria 5' loss in iron at constant frequencyvaries substantially as the 1.6 power of the induction. Thisapproxii'nate exponent of. 1.6 diftors somewhat for ditl crent-sanu'ilesof sheet The action of mydevice may be more readily understood from thefollowing analogy: assuming that a small transformer has been carefullytested on a sine wave by the usual methods, at the working voltage ofone of the windings of a large transformer for which a sine wave ironloss is desired and a record of the watts iron loss in the smalltransformer is found to be (L) at the voltage (V) if the smallthanstormcr is connected in multiple with the larger transformer, andboth are supplied with energy from a generator having a peaked wave or aflat wave characteristic. the iron loss on the small transformer at thesame voltage (V). indicated by an ordinary voltmeter would have adifferent value which may be designated by (L'l. The discrepancy justspecified is dependent upon the fact that the usual voltmeter indicatesa root-meansquare value of the, instantaneous electromotive forces whilethe iron loss is made up ol? a hysteresis loss. which depends upon theaverage value of the instantaneous electromotive forces and an eddycurrent loss which depends upon the root-nican-sqiiarc value of theii'istantai'icous electromotive forces, consequently, in order to obtainthe sine Wave loss of the, large transformer, the voltage of the circuitmust be varied until theloss (L) is indicated for the small transformer.

My device corresponds to the small. transformer, and is so combined witha \vattmeter mechanism and so calibrated on a sine Wave that it is onlynecessary to connect it in the circuit as indicated in the diagram ofFig. 2 the transformer* 2:") representing the large t ansl ormer to betestedl and to adjust the voltage of the. supply circuit until theinconnection, as Well as an adjustable construment pointer indicates avaluecorre-- sponding to the standard voltage of the transformer windingto which it is connected.

When extreme accuracy is required, as in very careful laboratory tests,the arrangement shown in. Fig. 3 may be employed which will give a.theoretically correct rcsult. This method consists in correcting theform factor of the voltage waves to 1.11 which is the form factor of asine Wave and then reading the loss. Thisis accomplished by introducinga variable inductance 32 in series with he supply circuit and connectingin an aluminum electrolytic cell 33 across the circuit between theinductance and the wattmeter, an ordinary voltmeter being connectedacross the circuit in multi ple with the iron loss voltmeter. Thevoltageimpressed upon the aluminum cell may be varied over a Wide range bymeans of an auto-transformer 3 connected across the circiiiit and havingan adjustable primary nection to the cell. T he inductance tends to peakthe wave of the line electromotive force and the aluminum cell, which isWorking above its critical voltage, short-circuits or filters out thepeaks until the form'factor is 1.11. That is to say, the effect of thein ductance and the aluminum cell are opposed to each other as far asthe form factor is concerned and adjustingthe inductance 32 and theauto-transformer 34: until the readings of the iron loss voltmeter andthe ordinary voltmeter agree, the form factor of the impressedclectromotive force is made to correspond to a sine wave being 1.11.

While this method does not necessarily give a sine wave for the test itgives a Wave having the same form filCli0l2- I claim as my invention:

1 A measuring instrument comprising relatively movable mutually reactingcoils, a magnetizahlc core member having a wind ing connected. in serieswith one of the said coi the instrument to include the losses in all itscircuits.

A. measuring instrument comprising relatively movable mutually reactingcoils, a magnctiza-hle core member having a Winding connected in serieswith one of the said coils, and auxiliary coils for causing theindications ofthe instrument to include the losses in all of itscircuits.

3. A measuring instrument comprising relatively movable mutuallyreacting coils, a magnctizable core member having a winding connected inseries with one of the said coils, and an auxiliary coil supplementingthe latter coil and connected in series with theother coil.

4.1K i'ncasuring instrument comprising relatively movable; mutuallyreacting coils, a magnctizablc core member having a Winding connected inseries with one of the said coils, and an auxiliary coil supplementingthe latter coil and connected in series with the other coil, themutually reacting coils and the devices in series therewith beingconnected in parallel relation.

1 measuring instrument comprising relatively movably mutually reactingcoils,

a magnetizablc core member having a winding connected in series with oneof the said coils, a plurality of scales, a pointer movable relativelythereto, and means for causing the pointer to indicate upon the scalesboth the main quantity measured by the instrumcnt and the energy lossesin all of the circuits of the instrument.

3, A measuring instrument comprising relatively movable mutuallyreacting coils, a magnetizable core member having a wind ing connectedinserics With one of the said coils, an auxiliary coil supplementing thelatter coil and connected in ser es With the ls, and means for causingthe indications other coil, a pointer and a plurality of s is upon\vliichTthe pointer indicates both the mau1 quantity measured by theinstrument and the losses in all of instrumen 7. In a measuringinstrument, the combination with stationary and movable coils, of amagnetizahle core member having a Winding connected in series with thesaid stationary coils, and an auxiliary coil con nected in series withthe said movable c l and supplementing the action oi? said stationarycoils an amount proportional. to the current traversing, said movablecoil.

8. The combination with an alternating current supply circuit and aninductive derice, to he tested, connected. thereto, of a measuringinstrument comprising; pluralitv of movable and stationary coils, anauxiliary inductive device connected in with one of the said coils, anauxiliary coil, and means for connecting the said coils so that theil'istrumcnt will indicate its losses.

9. The combination with an alternatingcurrent supply circuit and aninductive derice to he tested connected thereto, of a, measuringinstrument comprising" an auxiliary inductive device having known sineWave losses at the normal voltage of the device under "test, means foradjusting the actual voltage applied to said device under test and tosaid measuring instrinnent, and means for ineasu-rino' the losses in theinducti re device under test.

10. The combination with an alternating current supply circuit and atransformer to be tested connected thereto, of an electric measuringinstrument col: prising an auxiliary transformer having known sine Wavelosses at the normal voltage of the trans lormcr under test andstationary and morable coils reacting on each other, means for adjustingthe actualvoltageapplied to the transformer under test and to theireasuring instrument, and. means for measuring the losses in. thetransformer under test.

I1. The combination with an alternatingcurrentl supply :circuit and atransformer to he testcl connected thereto, of an electric measuringinstrument comprising an auxiliary transformer having known sine Wavethe circuits of the losses at the normal voltage of the transformerunder test, and stationary movable coils reacting on each other and mechanically independent of said auxiliary transformer, one of saidreacting coils being connected in series W'th said auxiliarytranstformer and the other in shunt to the first named coil and saidauxiliary transforflier, means for adjusting the actual voltage appliedto the transformer under test and to the measuring; instrumen and meansfor mczusuring the losses in the transformer under test.

12. The method of testing transformers 4a. ivo, cot? that consists inconnecting transformer to he tested to an alter-11a current supplycircuit in multiple circuit relation to an auX-- iliarj. transformer,having known sine Wave losses at the normal voltage of the trans formerunder test, "varying the actual roltapplied to both transiiorn'iersuntil the known sine Wave losses are expended in the auxiliarytranslfori' er and measuring the i ,J' in the main traiislformcr.

13, The combination with. an alternating current supp v circaiit and.,atransformer to he tested hair a Winding connected. tl1ci.'eto, of ameasuring instrument comprising an a uxilia rv transformer having aWimling con nected to said supply circuit and. having known sine wavelosses at the normal voltage of the transformer under-test, means for adjusting the actual VOltu C: applied to said transformer under test andto said 1neastiring instrument, and a Wattnietcr for measuring thelosses in the transformer under test.

14, The method of testing transformers WlllCll consists 111 adjustingthe voltage of the suprl; circuit to such a, value that the power codined in. a calibrated inductive device corresponds to the iron or coreloss in said inductive device at the stam'lard voltage otjthetransformer when said inductive derice is connected. to asup plv circuithaving a, sine wave electromotive force characteris tic, applying theadjuz-s cd voltage to the transformer and determining the iron or Mtherein.

15. The thod of testing transformers that consis a comiectimg thetransfer-nicer to he tested to an alternating current supply circuitlinmultiple circuit relation. to a calihrated inductive device having knownsine Wave losses, varying the actual voltage ap-- plied to both thetransformer and the inductivc device until the known sine wave lossescorresponding to the normal voltage of the transformer under test areconsumed in the other, magnetically independent of the core member andso connected and associated with the Winding as to eilect a. sine Wavevoltage indication proportional to the losses in the core member.

18, An iron loss voltmeter comprising a magnetizahle core member, aWinding thcrcfor, relatively movable coils reacting on. each other andmagnetically independent of the core member, one of said reacting coilsbeing lOl memos core member,

In testimony whereof, T. have hereunto subscnibed my name this 22nd dayof May,

LEWIS W. @HUBB. Witnesses: a

R. J DEARBORN, B. B. HINEs.

